This study is aimed at: 1) determining the basic physiological events in the process of exocrine pancreatic secretion in the living animal, the mechanisms by which this secretion is controlled, and (2) investigating the possible perturbations of these events in diseases such as Cystic Fibrosis. The approach is to conduct microelectrode and microsampling determinations of ion activities at various sites within the ductal system of the anesthetized rabbit. The experiments will also employ radioisotopic fluxes, perfusion techniques, metabolic and transport system poisons as well as hormonal stimulation of secretion. Consequently, the investigation will be conducted under experimental conditions that will allow us to explore the fundamental transport and control mechanisms responsible for pancreatic electrolyte and water secretion. Other studies are planned to investigate the role of perturbations in the secretion of calcium and other pancreatic juice constituents as well as serum or sweet-borne "Cystic Fibrosis" factors on secretion by the "normal" pancreatic ductal system. Techniques for the construction and use of micro-pH and pCO2 electrodes have already been developed as well as an in situ rabbit pancreas preparation.